Piezo-electric crystal apparatus



June 10, 1930. R. H. WORRALL PIEZOELEC'I'RIC CRYSTAL APPARATUS 3 Sheets-Sheet 1 Filed Feb. 25, 1928 gwuemtoz Robert 1/. Worrall MOIM June 10, 1930.

R. H. WORRALL PIEZOELECTRIC CRYSTAL APPARATUS I5 Sheets-Sheet 3 Filed Feb. 25, 1928 gwwznlov Habcri H Worrall Patented June 10, 1930 UNITED ROBERT E. WOBRALL, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB, BY MESNE ASSIGNMENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALI- romrm PIEZO- ELECTBIC CRYSTAL APPARATUS Application filed February 25, 1928. Serial No. 257,074.

My invention relates broadly to piezo electric crystal apparatus and more particularly to a piezo electric crystal holder.

One of the objects of my invention is to provide a construction of p ezo electric crystal holder wherein temperature changes outside of the holder have a minimum effect upon the temperature of the crystal within the holder for avoiding any tendency of frequency variation.

Another object of my invention is to provide a construction of iezo electric crystal holder having a rigid ase structure upon Y which a piezo electric crystal element may be 16 positioned by diametrically opposed elements which extend into slots at opposite sides of the piezo electric crystal element.

Still another object of my invention is to provide means for centering an upper elec trode with respect to .a piezo electric crystal element within a crystal holder, which elec trode is free to move vertically, but is prevented from sidewise movement.

A further object of my invention is to provide a construction of piezo electric crystal element for mounting within a crystal holder where the piezov electric crystal element is slotted at diametrically opposite edges to receive pins which protrude into the slots for centering the piezo electric crystal element with respect to a piezo electric cr stal holder.

Other and further objects 0 my invention reside in the construction of a piezo electric crystal holder described in the following specification and set forth in the accompanyingi drawings wherein:

igure 1 is a perspective view of'the piezo I electric crystal holder with the casing partially broken away to illustrate the interion arrangement of the piezo electric crystal holder; Fig. 2 is a perspective view of the piezo electric crystal holder with the casing in place; Fig. 3 is a plan view of the interior arrangement of the piezo crystal holder; Fig. 4 is a side elevation of the assembled parts of the piezo electric crystal holder with the casing and upper electrode guide shown in cross-section and broken away; Fig. 5 is an end view of the interior parts of the piezo electric crystal holder with the casing and a portion of the upper electrode guide illustrated in cross-section; Fig. 6 is a fragmentary perspective view of the crystal of the piezo electric crystal holder mounted in position on the base plate of the piezo electric,

crystal holder; and Fig. 7 is a lan view looking at the lower surface of the ase plate of the piezo electric crystal holder.

Referring to the drawings in detail, reference character 1 designates the base plate upon which the piezo electricelement 16 is mounted. The base plate 1 has a ribbed ortion 2 with reenforced ribs 3 exten g through the area of the lower ortion of the base as illustrated more clear y in Fig. 7. The base 1 is drilled and tapped as represented at 4 to receive the machine screws 6 which retain the cover 5 in position and provide means for establishing an electrical connection with the lower surface of the piezo electric crystal element 16. The basel is rovided with two portions 7 which taper rom the end of the plate to the center thereof oining the flattened portion 8 of the surface 1. The flattened portion 8 provides a central bearing surface for the iezo electric crystal element 16. At diametrically opposite positions on the central portion 8 I provide retainer members 9 and 11 each having pins 15 and 14 projecting therefrom and extending toward each other. The retainer member 9 is secured to the flattened zone 8 of supporting base 1 by screw members 10. The retainer member 11 is secured to the flattened zone 8 by screws 12. The pins 14 and 15 project into slots 17 and 18, respectively, cut in the piezo electric crystal element 16 as represented in Fig. 6.

I have found it necessary to secure the crystal at two points only where there is no movement lengthwise while the crystal is oscillating. This position was found to be in the exact center of the len h of the c stal and to correspond to a no al point 0 the crystal. The slots 17 and 18 are very carefully formed on each side of the exact center line and of such a width that pins 14 and 15 substantially fill the slots leaving no lost motion. In order to establish contact with the upper surface of the piezo electric crystal element I provide a yoke member 19 which is supported on pedestals 20 and 21 and secured by means of screws 22 and 23 ad acent one side of the base 1. Yoke 19 is a ertured at 24 and 24 adjacent opposite en s thereof for receiving pins 25 and 26 which extend vertically from the upper contact late 18. The plate 18 floats freely up and own upon the top of the crystal 16 but is otherwise maintained in positionwith respect to the crystal. The oke 19 carries a central screw threaded member 27 secured in position by means of nut 28. A hea mica sheet 31 is provided and secured injiiie frame 32 of cover 5 and serves as a support in which the screw threaded member 27 is positioned by means of nuts 29 which are screwed on opposite sides of the mica sheet 31. The upper extremity of the screw threaded member 27 is slotted as represented at for receiving a terminal tip 30 for connecting the piezo electric crystal apparatus in an electrical circuit. The casing 5 is provided at one side thereof with a well 33 for receiving the bulb of a thermometer for the purpose of recording the temperature of the base upon which the piezo electric element is supported. A flexible connection exfollows:

tends from the upper electrode 18 through the medium of pin 25 to the central terminal 27 from which connection may be made extcriorly of the casing. Connection to the lower contact plate is made by grounding to the base structure 1.

The piezo electric crystal apparatus of my invention has been found to be extremely practical in its construction, manufacture, amembly and operation, and while I have described one of the preferred embodiments of my invention, I desire that it be understood that modifications may be made andthat no limitations upon my invention are intended except as imposed by the scope of the append ed claims.

What I claim as new and desire to secure by Letters Patent of the United States is as 1. A piezo electric crystal holder comprising a mounting plate having a flat surface,

a cover member secured to said mounting plate, a piezo electric crystal element supported by said mounting plate upon said flat surface, means positioned transversely of said mounting plate and directed toward said piezo electric crystal element for maintaining said piezo electric crystal element in po-' sition, an electrode positioned in floating contact on the upper surface of said piezo electric crystal element, and means extending from one side of said mounting plate for centering said electrode with respect to said piezo electric crystal element.

2. Piezo electric crystal apparatus comprising a rectangular mounting plate, a piezo electric crystal supported from said lli0ll11t mg plate, said piezoelectric crystal being slotted at o posite sides thereof, a pair of retainer mem ers supported by said mounting plate and extending into the slots formed in said piezo electric crystal element for centering said piezo electric crystal element with respect to said mounting plate.

3. In a piezo electric crystal apparatus, a mounting plate, a piezo electric crystal element having its lower surface positioned in contact with said mounting plate, a pair of retainer members carried transversely of said mounting plate, pins extending from each of said retainer members, said piezo electric crystal element being slotted at opposite edges thereof for receiving said pins for centering said piezo electric crystal element with respect to said mounting plate, and means for establishing electrical connection with the upper surface of said piezo electric crystal element.

4. In a piezo electric crystal apparatus a piezo electric crystal element, a holder for said piezo electric crystal element comprising a metallic supporting plate, a system of transverse ribs on a surface of said supporting plate for preventing said plate from warping, a casing secured to the peripheral edge of said supporting plate and providing an enclosure for said piezo electric crystal element, and a well carried by said casing for receiving a thermometer therein for determining the temperature interiorly of said casing adjacent said piezo electric crystal element.

5. A piezo electric crystal apparatus comprising a supporting base, a-piez o electric crystal element having its lower surface resting in contact therewith, an electrode floating on the upper surface of said piezo electric crystal element, a bridge member consisting of a substantially U shaped flat strip supported at its extremities on said supporting base, a terminal protruding vertically from,

the center of said bridge member, and means on the opposite sides of said terminal and carried by said bridge member for guiding said 3 upper electrode in osition with respect to the upper surface 0 said piezo elect-r10 crystal element.

6. Piezo electric crystal apparatus comprising a supporting base member, a piezo electric crystal element having its lower surface resting in contact with said su porting base member, a casing housing said piezo electric crystal element and connected with the eripheral edge of said supporting base memer, an electrode floating upon the upper surface of said piezo electric crystal element, a member extending from one side of said supporting base member to a position centrally over said electrode, and a plurality of pins protruding vertically from said electrode and passing through apertures in said centrally positioned member for maintaining said electrode in position with respect to said piezo electric crystal element free to move vertically in accordance with vibration of said piezo electric crystal element.

7. A piezo electric crystal holder comprising in combination, a member having a flat surface, a flat rectangular plate of material possessing piezo electric properties disposed upon the flat surface of said member, said plate having a longer longitudinal axis than its transverse axis, said plate having slots formed on each edge at diametrically opposite points along said transverse axis and pins disposed upon said flat surface, said ins being disposed in the slots of said p ate for preventing lateral displacement thereof. x,

8. A piezo electric crystal holder comprising in combination, a member having a flat surface, a flat piezoelectric plate, said plate having notches cut into its sides said notches being disposed at nodal points along said sides and means positioned upon said member or engaging said notches and preventing lateral movement of said plate upon said member.

'9. A piezo electric crystal holder comprising in combination, a member having a smooth flat surface,means on said member for preventing warping of said flat surface, a piezo electric plate adapted for frequency control of the oscillations of a high frequency generator positioned upon the flat surface of said member, said iezo-electric plate having notches cut into tl ie sides thereof at points corresponding to the nodal points of these sides and means associated with said member for engaging in the notches of said plate for preventing lateral movement of said plate with respect to said member.

in such manner that said floating electrode floats freely on said guiding pins;

12. In piezo electric crystal apparatus, a metallic mounting plate, a piezo electric crystal element having its'lower surface 0- sitioned in contact with said mountin p to and being notched on each of the two ongest edges thereof substantially at the mid-pomts of said longest edges, a pair of retainer members attached to said mounting plate, pins extending from each of said retainer members toward each other and so positioned and of such size as to en ageand substantially fill said notches in sai piezo electric crystal ,ele

ment, and means for establishing electrical connection with the upper surface of said piezo electric crystal e ement.

ROBERT H. WORRALL.

10. In a piezo electric crystal holder the V combination of a su porting member having a flat surface, ribs 'sposed upon one of the surfaces of said supporting member for preventing said flat surface from warping, a piezo electric crystal adapted for frequency control of a high frequency oscillation generator, said piezo electric crystal being positioned upon said flat surface, pins detachably mounted upon said supporting member, said pins engaging in notches in the vertical sides of said piezo electric crystal, said notches being disposed along said sides at points corresponding to nodal points of said piezo electric crystal.

11. Piezo electric crystal apparatus comprising a metallic plate, a piezo electric crystal element having its lower surface resting in contact'with the upper surface of said metallic plate, a floating electrode in contact with the upper surface of said piezo electric crystal, a supporting member attached to said metallic plate and positioned above said floating electrode, said floating electrode being provided with guiding pins extending upwardly therefrom, said supporting member being apertu'red to receive said guiding pins 

